1. Field of the Invention
The present invention relates to a color liquid crystal display panel that operates in a reflection mode and in a transmission mode.
2. Description of the Background Art
FIG. 4 and FIG. 5 are cross-sectional views schematically illustrating semi-transmissive color liquid crystal display devices of Conventional Examples 1 and 2, respectively, each of which operates in a reflection mode and in a transmission mode.
The process of manufacturing a liquid crystal display device of FIG. 4 will now be described. A color filter layer 3 is formed on a viewer-side glass substrate 2 and subjected to an overcoat process using a spin coating method, after which a sputtered transparent electrode 4 is patterned. An alignment film 5 is formed thereon using a roll coater method and subjected to a rubbing treatment.
An SiO2 film and a thin aluminum film are sputtered on a light-source-side glass substrate 10, and a transflective film 9 (e.g., a reflective film having slits therein) is formed by photolithography. A transparent electrode 8 and an alignment film 7 are formed as described above, after which a rubbing treatment is performed. The substrate 2 and the substrate 10 are attached together so as to oppose each other, and a liquid crystal material is injected into the gap between the substrates 2 and 10 to form a liquid crystal layer 6. Then, polarizing plates 1 and 11 are provided on the viewer side of the substrate 2 and on the light source side of the substrate 10, respectively, and the light source 12 is provided, thus obtaining the liquid crystal display device as illustrated in FIG. 4.
The process of manufacturing a liquid crystal display device of FIG. 5 will now be described. A transparent conductive film is sputtered on a viewer-side glass substrate 2 and patterned into a transparent electrode 4 by photolithography. An alignment film 5 is formed thereon using a roll coater method and subjected to a rubbing treatment.
An SiO2 film and a thin aluminum film are sputtered on a light-source-side glass substrate 10, and a transflective film 9 (e.g., a reflective film having slits therein) is formed by photolithography, on which a color filter layer 3 is formed. A transparent electrode 8 and an alignment film 7 are formed as described above, after which a rubbing treatment is performed. The substrate 2 and the substrate 10 are attached together so as to oppose each other, and a liquid crystal material is injected into the gap between the substrates 2 and 10 to form a liquid crystal layer 6. Then, polarizing plates 1 and 11 are provided on the viewer side of the substrate 2 and on the light source side of the substrate 10, respectively, and the light source 12 is provided, thus obtaining the liquid crystal display device as illustrated in FIG. 5.
The liquid crystal display devices of FIG. 4 and FIG. 5 use the transflective film 9 in order to realize both a reflection-mode display function using ambient light coming from the viewer side and a transmission-mode display function using light from the light source (hereinafter referred to as “light-source light”). The transflective film 9 may be a reflective film having slits therein or a half mirror.
The liquid crystal display devices of Conventional Examples 1 and 2 illustrated in FIG. 4 and FIG. 5 have the following problems. Light (reflected light) 16 used in the reflection mode is the ambient light coming from the viewer side, passing through the color filter layer 3, reflected by the transflective film 9 and passing again through the color filter layer 3 to exit the device toward the viewer. In contrast, light (transmitted light) 17 used in the transmission mode is the light from the light source 12, passing through the color filter layer 3 only once to exit the device toward the viewer. Therefore, the reflected light 16 passing through the color filter layer 3 of the same color twice and the transmitted light 17 passing therethrough only once will have significantly different saturations from each other. Moreover, in these liquid crystal display devices, the transmittance of the color filter layer 3 is set to be high, whereby colors are hardly recognized in the transmission mode.
Japanese Laid-Open Patent Publication No. 2000-321564 discloses a liquid crystal display device capable of eliminating the difference in saturation between the reflection mode and the transmission mode. The liquid crystal display device includes two color filter layers provided on opposite sides of the reflection plate. Therefore, the ambient light and the light-source light both pass through a color filter twice, whereby it is possible to display clear images without having a difference in saturation between the reflection mode and the transmission mode.
However, a photolithography process is employed in most cases in the color filter formation, and the photolithography process needs to be performed for each of color filter layers of different colors, i.e., red, green and blue. Therefore, the above liquid crystal display device requires a complicated manufacturing process and will be very expensive.